GB2118065A

GB2118065A - Waste material shredder

Info

Publication number: GB2118065A
Application number: GB08304006A
Authority: GB
Inventors: Takefumi Hatanaka
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-02-12
Filing date: 1983-02-14
Publication date: 1983-10-26
Also published as: US4690340A; US4776525A; GB8304006D0; US4844366A; DE3305063A1; GB2118065B

Description

1 GB 2 118 065 A 1 SPECIFICATION Waste material shredder - 10 1

Background of the Invention

Various types of waste material shredder are in use at the present time. These are used primarily for shredding documents in order to destroy the information content therein. However various other materials may be subjected to shredding, such as for example computer punch cards, printed circuit substrates, etc. Such waste material shredder can be broadly divided into two types, i.e. strip type shredders and cross-cut shredders. The strip type shredders act to cut sheets of waste material into elongated longitudinal strips, by a shearing action, while the cross-cut shredders cut the sheets of waste material into small chips, or very short strips. From 80 the aspect of maximum destruction of any information contained in the waste material, and for minimizing the volume of the shredded output material, the cross-cut type of shredder is preferable. However a major problem which has arisen with prior art types of cross-cut shredder is that the shredded chips produced by the shredder tend to gradually accumulate within the mechanism, over a period of time, and to eventually cause the mechanism to be jammed, so 90 that it becomes necessary for the user to periodically clear out such blockages from the shredder. This is extremely inconvenient, and is a major disadvantage of prior art cross-cut shredders by comparison with the mechanically simpler strip type shredders.

More specifically, a cross-cut shredder generally comprises a pair of rotating shafts with their axes of rotation parallel to one another, with sets of cutter disks fixedly mounted on each shaft, and mutually meshing. Spacer members are fixedly mounted between the cutter disks of each shaft, to maintain a fixed separation between the cutter disks, and teeth are formed on the peripheries of the cutter disks. When such a 105 shredder is operated over a long period of time, the shredded chips which are produced by a cutting action of the teeth and shearing between the cutter disks are not entirely removed from the mechanism,'and gradually accumulate between the spacer members. As time elapses, this accumulation will increase to such an extent that the cutter disks can no longer rotate, and so the chips must be cleared out by the user.

With a waste material shredder according to the present invention, a special configuration for the cutter disks is employed, whereby the shredded chips are completely removed from the cutter mechanism immediately after they are produced, so that the problem described above is entirely eliminated. Thus a waste material shredder according to the present invention presents substantial advantages over prior art shredders with respect to ease of maintenance and reliability of operation.

Summary of the Invention

According to the present invention, there is provided a waste material shredding apparatus for converting sheets of waste material into small chips, comprising: a supporting frame; first and second counter-rotating cutter rollers mounted rotatably in said supporting frame; first and second sets of spacer plates fixedly mounted on said supporting frame; said first and second cutter rollers comprising first and second roller shafts respectively, disposed to be mutually parallel, and first and second sets of cutter disks fixedly mounted coaxially along said first and second shafts respectively with adjacent ones of said first and second sets of cutter disks being separated from one another by one of said first set of spacer plates and one of said second set of spacer plates respectively, with said first set of cutter disks being disposed such as to fit closely between said second set of cutter disks, each of said cutter disks having a plurality of cutter teeth formed at angular spacings around the periphery thereof and protruding radially outward, and further having a plurality of chip clearance protrusions formed around said periphery protruding radially outward with each of said chip clearance protrusions being positioned intermediate between adjacent ones of a pair of said cutter teeth, each of said cutter teeth having a sharp cutting edge formed at the tip thereof with said cutting edge being aligned substantially parallel to the axes of said cutter rollers, and each of said chip clearance protrusions having a leading face formed on the leading portion thereof with respect to the direction of rotation of the corresponding cutter disk, said leading face having a substantially linear profile and forming an oblique angle with the preceding portion of the periphery of said cutter disk as viewed along the axis of rotation of said cutter disk, with the relative positions of said first and second sets of cutter disks being disposed such that each of said cutter teeth on a cutter disk of one of said cutter rollers penetrates a sheet of waste material to be shredded, for thereby cutting a transverse perforation therein, at an instant when the tip of said cutter tooth is immediately adjacent to a portion of one of said leading faces of one of said chip clearance protrusions on an adjacent one of the other set of cutter disks, with said sheet thereafter advancing between said first and second cutter rollers to be sheared longitudinally between said first and second sets of cutter disks and thereby converted into a plurality of small chips.

Brief Description of the Drawings

In the drawings, Fig. 1 is a cross-sectional view of the cutter rollers and spacer plates of an embodiment of a waste material shredder according to the present invention, taken in a plane perpendicular to the longitudinal axes of the cutter rollers; Fig. 2 is a partial cross-sectional view in plan of 2 GB 2 118 065 A 2 the cutter rollers and spacer plates of the embodiment of Fig. 1; Fig. 3 is a cross-sectional view of the cutter rollers and spacer plates of the embodiment of Fig.

1, illustrating the cutting action applied to a sheet of waste material; and Fig. 4 is a partial oblique view of an alternative configuration for the cutter teeth of a waste material shredder according to the present invention.

Description of the Preferred Embodiments

Referring now to the drawings, Fig. 1 shows a cross-sectional view of the cutter rollers and spacer plates of an embodiment of a waste material shredder according to the present invention, as seen along the longitudinal axes of the cutter rollers, while Fig. 2 is a partial cross sectional view in plan of these cutter rollers and spacer plates. The drive means for rotating the cutter rollers and the means for directing sheets of 85 waste material to be cut are not shown in the drawings. Numerals 10 and 11 denote a pair of roller shafts of a pair of cutter rollers 8 and 9 respectively, which are rotatably mounted at ends 18 and 19 in bearings 20 and 21 respectively, and 90 rotate in opposite directions to one another. The cutter rollers 8 and 9 are mounted adjacent to one another with their longitudinal axes aligned parallel to one another. Numeral 12 collectively designates a set of cutter disks which are mounted on roller shaft 10, and numeral 13 denotes a set of cutter disks which are fixedly mounted on roller shaft 11. Numeral 14 collectively designates a set of spacer plates which are fixedly attached to supporting member 100 16 (and an opposing supporting member, not shown in the drawings) by longitudinal members 14a and 14b with the spacer plates 14 and cutter disks 12 being arranged in an alternating manner as shown, so that each pair of cutter disks is separated by a spacer plate. Similarly, a set of cutter disks 13 are fixedly mounted on roller shaft 11, and alternate with spacer plates 15. The cutter disks 12 of cutter roller 8 mesh with cutter disks 13 of cutter roller 9, as shown in the drawings.

The cutter disks 12 and 13 are restrained from rotating with respect to roller shafts 10 and 11, by providing a hexagonal cross-section external contour on mounting portions 20 and 21 of roller shafts 10 and 11 respectively, and providing corresponding hexagonal apertures in cutter disks 12 and 13 for mounting on the shafts, as shown in Fig. 1. Circular apertures are formed in the spacer plates 14 and 15, having a diameter which is slightly greater than the circumscribing circle of the hexagonal cross-sectional contour of roller shafts 10 and 11, since the spacer plates are held stationary.

Each of the rotating cutter disks 12 and 13 is provided with a set of cutter blades, denoted as 12a and 13a respectively, which protrude radially outward from the periphery thereof, and which are arranged at regular spacings around the periphery.

Each of cutter disks 12 and 13 is further provided with a set of chip clearance protrusions, designated as 12b and 13b, respectively, which also protrude radially outward from the periphery of each cutter disk, with the chip clearance protrusions alternating with the cutter blades as shown, i.e. with a chip clearance protrusion separating each pair of cutter blades.

In the present embodiment, the cutter blades have a sharp chisel shape, which is triangular as view in cross-section as seen in Fig. 1. In other words, each of the cutter blades has a laterally extending cutting edge, which perforates the sheets of waste material with a very low amount of resistance to that perforation, as described in greater detail hereinafter.

Each of the chip clearance protrusions has a trapezoidal shape as viewed in cross section, in the present embodiment, as seen in Fig. 1. It is an essential feature of the present invention that eading face of each of the chip clearance protrusions (i.e. the face which reaches the waste material immediately after a preceding cutter blades, as the corresponding cutter disk rotates) forms an oblique angle with a face that is substantially tangential to the periphery of the cutter disk. Thus in the present embodiment, the leading face 12c of cutter disk 12 forms an oblique angle 0 with the tangential face 12d. It should be noted that it is possible to form the chip clearance protrusions with a more curved and rounded shape than that of the present embodiment, or to form each of the chip clearance protrusions substantially in the form-of a hemisphere, as viewed in cross-section.

The meshing relationship between the sets of cutter disks 12 and 13 of the cutter rollers 8 and 9 can be clearly understood from Fig. 2. The cutting operation of the present embodiment will now be described in great detail with reference to Fig. 3. Here, numeral 24 denotes a sheet of waste material which is to be shredded, and which is inserted vertically from the top of the diagram downward between the sets of cutter rollers 8 and 9, being directed by the shape of the upper portions of the spacer plates 14 and 15 to be drawn down by the action of the mutually meshing sets of cutter disks 12 and 13. The sheet of waste material first meets the leading sloping face 12c of one of the chip clearance protrusions 12b of cutter disks 12, and then a lateral slit perforation is formed in the waste material sheet 24 by cutter blade 13a of the opposing rotating cutter disk 13. At this time, the latter leading sloping face 12c, due to the oblique angle at which it is set as described above, acts to guide the waste material sheet 24 such that blade 13a is thrust into the sheet in a direction substantially perpendicular to the plane of the sheet 24. As a result, a slit 26 is cut in the waste material sheet 24 with a very low level of resistance to that cutting action. Next, as a result of the meshing rotation of the sets of cutter disks 12 and 13, waste material sheet 24 is cut into strips in the longitudinal direction (i.e. in the direction of travel of the sheet), and as a result of this, in conjunction 1 1 3 G13.2 118 065 A 3 with the formation of slit 26, shredded chips 28 and 30 are formed. As the cutter disks 12 and 13 continue to rotate in the intermeshing condition, the shredded chips 28 and 30 are pushed outward by the cps 12b of cutter disk 12, and thereby is separated from the cutter mechanism. Since the leading face 12c of chip clearance protrusion 1 2b meets the chip 30 such that the latter face makes an oblique angle with the chip, chip 30 is pushed out with a low level of resistance being developed to this removal. In this way, chip 30 is reliably separated from the cutter blades and drops down out of the cutter mechanism.

Although the cutting and chip removal operation has been described in the above for a single sheet of waste material, for simplicity of description, in actual practice a plurality of waste material sheets will be shredded simultaneously.

It can thus be understood from the above description that a waste material shredder according to the present invention effectively removes shredded chips from the cutter mechanism immediately after these chips have been formed, by means of chip clearance protrusions formed on the cutter disks of the cutter rollers, with the effectiveness of this chip clearance function being enhanced by a suitable shape for these chip clearance protrusions. It can be further understood that these chip clearance protrusions also serve to direct sheets of waste material in a manner ensuring efficient lateral perforation of the waste material sheets by the cutter blades of the cutter rollers, thereby enhancing the efficiency of the overall shredding operation and reducing the power consumption of such a shredder.

Fig. 4 is a partial oblique view illustrating an alternative configuration of the cutter blades of a waster material shredder according to the present invention, as compared with the chisel-shaped cutter blades of the embodiment described above. 105 In the embodiment of Fig. 4, triangular incisions 36 are formed in each of the cutter blades 34 of a cutter disk 32, so that a plurality of sharp teeth are formed on each of the cutter blades. Such a configuration for the cutter blades is advantageous for certain types of waste material.

It should be noted that, in addition to the shape of the leading sloping edge of each of the chip clearance protrusions of the cutter disks of a waste material shredder according to the present invention being an important basic feature thereof, the relative positions of the cutter disks of one cutter roller with respect to the cutter disks of the opposing roller are also extremely important. More specifically, these relative positions must be 120 arranged such that, as illustrated in Fig. 1, each of the cutter teeth of one cutter disk, e.g. each of teeth 13a of cutter disk 13, comes into position for perforating a waste material sheet at an instant when the central region of a leading sloping face 125 (e.g. 12c) of a chip clearance protrusion (e.g. 12b) is positioned adjacent to the tip of the latter cutter tooth. It has been found that this ensures extremely effective operation of the shredder.

Although the present invention has been described in the above with reference to specific embodiments, it should be noted that various changes and modifications to these embodiments may be envisaged which fall within the scope claimed for the present invention, as set out in the appended claims. Thus, the above description should be interpreted in a descriptive and not in a limiting sense.

Claims

1. A waste material shredding apparatus for converting sheets of waste material into small chips, comprising: a supporting frame; first and second counter-rotating cutter rollers mounted rotatably in said supporting frame; first and second sets of spacer plates fixedly mounted on said supporting frame; said first and second cutter rollers comprising first and second roller shafts respectively, disposed to be mutually parallel, and first and second sets of cutter disks fixedly mounted coaxially along said first and second shafts respectively with adjacent ones of said first and second sets of cutter disks being separated from one another by one of said first set of spacer plates and one of said second set of spacer plates respectively, with said first set of cutter disks being disposed such as to fit closely between said second set of cutter disks, each of said cutter disks having a plurality of cutter teeth formed at angular spacings around the periphery thereof and protruding radially outward, and further having a plurality of chip clearance protrusions formed around said periphery protruding radially outward with each of said chip clearance protrusions being positioned intermediate between adjacent ones of a pair of said cutter teeth, each of said cutter teeth having a sharp cutting edge formed'at the tip thereof with said cutting edge being:aligned substantially parallel to the axes of said cutter rollers, and each of said chip clearance protrusions having a leading face formed on the leading portion thereof with respect to the direction of rotation of the corresponding cutter disk, said leading face having a substantially linear profile and forming an oblique angle with the preceding portion of the periphery of said cutter disk as viewed along the axis of rotation of said cutter disk, with the relative positions of said first and second sets of cutter disks being disposed such that each of said cutter teeth on a cutter disk of one of said cutter rollers penetrates a sheet of waste material to be shredded, for thereby cutting a transverse perforation therein, at an instant when the tip of said cutter tooth is immediately adjacent to a portion of one of said leading faces of one of said chip clearance protrusions on an adjacent one of the other set of cutter disks, with said sheet thereafter advancing between said first and second cutter rollers to be sheared longitudinally between said first and second sets of cutter disks and thereby converted into a plurality of small chips.

2. A waste material shredding apparatus according to claim 1, in which said each cutter 4 GB 2 118 065 A 4 tooth of a cutter disk on one of said cutter rollers cuts said transverse perforation in said sheet of waste material at an instant when said tooth is close to the midpoint of said leading face of said chip clearance protrusions on said adjacent cutter disk of the other cutter roller.

3. A waste material shredding apparatus 20 according to claim 1, in which the profile of each of said chip clearance protrusions forms three sides of a trapezoid, as viewed along the axis of rotation of the corresponding cutter disk.

4. A waste material shredding apparatus 25 according to claim 1, in which the profile of each of said chip clearance protrusions has a V-shape, as viewed along the axis of rotation of the corresponding cutter disk.

5. A waste material shredding apparatus according to claim 1, in which each of said cutter teeth has a profile in the form of a V-shape, as viewed along the axis of rotation of the corresponding cutter disk.

6. A waste material shredding apparatus according to claim 5, in which at least one notched portion is formed in the cutting edge of each of said cutter teeth.

J- Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1983. Published by the Patent Office Southampton Buildings, London, WC2A lAY, from which copies may be obtained.

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